Bruce Chapman Bruce Chapman - 4 months ago 29
C# Question

How to get Microsoft.AspNet.Http.HttpContext instance in Class Constructor using DI

I am building a throwaway application in MVC 6 and experimenting with different architectures for dependencies.

The problem I am facing is how to create a custom '

MyAppContext
' object specific to the Application. This would require some information from the
HttpContext
and some information from the database, and will be a request-scoped repository for application specific attributes. I want to pass the instance of the
HttpContext
into the constructor of the '
MyAppContext
'.

I have successfully created a '
DataService
' object with an
IDataService
interface using DI and this works Ok.
The difference with the 'MyAppContext' class is that it has two parameters in the constructor - the '
DataService
' and the
Microsoft.AspNet.Http.HttpContext
. Here is the MyAppContext class:

public class MyAppContext : IMyAppContext
{
public MyAppContext(IDataService dataService, HttpContext httpContext)
{
//do stuff here with the httpContext
}
}


In the startup code, I register the DataService instance and the MyAppContext instance:

public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
//adds a singleton instance of the DataService using DI
services.AddSingleton<IDataService, DataService>();
services.AddScoped<IMyAppContext, MyAppContext>();

}

public void Configure(IApplicationBuilder app)
{
app.UseErrorPage();
app.UseRequestServices();
app.UseMvc(routes => /* routes stuff */);
}


I am expecting the
HttpContext
parameter in the constructor to get resolved by DI.
When running the code, this is the exception I get returned:


InvalidOperationException: Unable to resolve service for type 'Microsoft.AspNet.Http.HttpContext' while attempting to activate 'MyAppContext'


I figure this is because there is no specific instance of
HttpContext
that this error is occurring, but I don't know how to register the
HttpContext
instance in DI. I added the line '
app.UseRequestServices();
' but this hasn't made any difference. I also tried a variant of:

services.AddScoped<HttpContext, HttpContext>();


But this fails because the second
HttpContext
is supposed to be an instance - I know it's not correct but haven't been able to work out what is.

So, in summary - how can I pass in the
HttpContext
object into the constructor of MyAppContext?

Answer

Inject IHttpContextAccessor in the constructor